Simulation Research Of Welding Structure Residual Stress And Distortion For Railway Vehicle

Welding is one of the key technologies in the manufacture of railway vehicle. It has been widely used in the production of the car-body, bogie and other core components. Welding residual stress and distortion which occur in welding process due to uneven heating bring unfavorable effect on the reliability of the railway vehicle and their service. As a result, welding residual stress and distortion forecasting becomes an important and urgent research topic in railway vehicles. Different numerical prediction methods are presented corresponding to two typical types of welded structures on railway vehicles. The distribution and variation trend of residual stress and distortion based on the experimental verification is analysed, using the finite element analysis software ANSYS and special software SYSWELD, Pam-Assembly. It is helpful to shorten the production cycle, so as to provide scientific basis for optimizing the welding process and learning welding principle further.The main contents of this paper are as follows:Firstly, present numerical simulation situation of welding residual stress and distortion at home and abroad are investigated. The reason for welding residual stress and distortion is analyzed. At the same time, basic principal of welding residual stress and distortion including temperature field theory, thermo-elastic-plastic theory and inherent strain theory are developed.Secondly, inherent strain method and "local-global" finite element method are brought forward to simulate welding distortion of large size, long weld, thin slab structutre in the railway vehicle. Taking a certain type of side wall in high-speed trains as study objects, welding distortion is simulated by transforming inherent strain into equivalent thermal loads on the welded seams and heat affected zone. This process requires only elastic finite element analysis. In the "local-global" finite element method, extract the mcroelements from local model and mapping it to the whole side wall by software Pam-Assembly. At last, the distortion of the side wall is simulated.Finally, according to the characteristic of multi-pass welding in railway vehicles, thermal cycle curve instead of transient heat source is put forward. Taking typical welding joint of schnabel as study objects, initially impose double ellipsoid heat source model to adjust the heat source and extract the average thermal cycle curve. In accordance with welding sequence, thermal cycle curve is applied to weld successively. The influence of preheating temperature and the weld number to welding residual stress and distortion in multi-pass welding process is studied.